Roll or buffer storage for a flat web material

ABSTRACT

The invention relates to a buffer storage for a flat web material ( 2 ), having at least two roller registers ( 3, 4 ) comprising a plurality of freely rotating rollers ( 11, 12 ) and displaceable relative to each other at least in one axis direction radial to the axis of the rollers ( 11, 12 ), for forming variable partial lengths or loops of the flat web material ( 2 ) between the rollers ( 11, 12 ) of the roller register, having at least one piston-cylinder arrangement ( 8 ), the cylinder chamber ( 10 ) thereof being able to be acted upon by a compressible pressure medium, such as compressed air, and acting like a pressure or gas spring between the at least two roller registers ( 3, 4 ) for generating a web tension of the flat material ( 2 ) guided through the buffer storage, and having a control device for applying a constant or substantially constant operating pressure of the pressure medium to the at least one piston cylinder arrangement ( 8 ).

The invention relates to a roll or buffer store according to the preamble of claim 1.

Roll or buffer stores for flat web materials, particularly for web-shaped packaging materials or films are known and are used in systems for processing the flat material, for example in packaging systems, to maintain a predetermined web tension by intermediate storage of in each case a variable length of the flat material. Buffer stores of this type comprise at least two roller registers which have, for example, a plurality of rollers arranged mutually parallel and spaced apart from one another, which are mounted freely rotatable in the roller registers and over which the flat web material is guided, forming a plurality of loops. The roller registers are arranged movable relative to one another, i.e. one roller register is provided, for example, fixed and the other roller register is movable, for example, pivotable in an axis direction radially to the rotation axis of the rollers. In order to tension the flat material between the roller registers, at least one element which acts as a spring is provided which is formed, in known buffer stores, inter alia, by at least one piston-cylinder arrangement (pneumatic cylinder) with at least one cylinder chamber to which the operating pressure of a compressible fluid in the form of compressed air can be applied, so that the piston-cylinder arrangement acts as a gas spring or compressed air spring.

A disadvantage of these known buffer stores is that, in the event of a fault and particularly on tearing of the flat web material, the full working pressure still acts in the cylinder chamber, so that the movable roller register which is no longer held back by the torn flat material moves more or less suddenly into the end position of the possible movement stroke or pivot stroke thereof, and this entails a significant risk of injury to operating personnel.

It is an object of the invention to provide a roll or buffer store which avoids this disadvantage and has significantly better operational safety. The solution to this problem is a roll store or buffer store configured according to claim 1.

The peculiarity of the buffer store according to the invention lies therein that, in a first condition of a first control valve arrangement, i.e. during normal operation, the at least one cylinder chamber of the at least one piston-cylinder arrangement is connected to a device for providing the operating pressure, and the first control valve arrangement can be switched, in the case of a machine standstill and/or a fault, into a second condition in which said control valve arrangement not only interrupts the connection of the at least one cylinder chamber to the device for providing the operating pressure, but also traps the volume of fluid or pressure medium present in the at least one cylinder chamber.

At the same time, a reduction of the pressure in the at least one cylinder chamber to a residual pressure significantly below the operating pressure takes place. This residual pressure is, for example, in the range of only 30% to 40% of the operating pressure. It is herein essential that the residual pressure is adjusted dependent on the mass of the pivot arm of the roll or buffer store.

Reduction of the pressure to the residual pressure is carried out via a relief valve which is also preferably switched with the first control valve arrangement and is configured so that said valve opens at a pressure above the residual pressure and brings about pressure relief for example by venting to the atmosphere and blocks at a pressure equal to or less than the predetermined residual pressure.

In the event of a machine standstill and/or a fault, tensioning of the flat material is very low, but sufficient for maintaining the proper running of the flat material through the buffer store is achieved with the residual pressure. By trapping the pressure medium in the cylinder chamber and by using the relief valve which is, for example, a safety valve adjusted to the residual pressure, it is also achieved that, in the event of tearing of the flat web material and the associated removal of the load on the movable roller register, although a slight movement of said roller register takes place due to the piston-cylinder arrangement acting as a gas spring or compressed air spring, the distance of this movement and the force exerted by the piston-cylinder arrangement are extremely small, particularly due to the expansion of the pressure medium trapped in the cylinder chamber and the associated further reduction of the pressure below the residual pressure.

Developments, advantages and possible applications of the invention are also disclosed in the following description of exemplary embodiments and in the drawings. All the features described and/or illustrated are fundamentally the subject matter of the invention either per se or in any combination, regardless of their grouping together in the claims or their back references. The content of the claims is also made a part of the description.

The invention will now be described in greater detail by reference to an exemplary embodiment illustrated by the drawings, in which:

FIG. 1 shows, in a simplified illustration, a roll or buffer store according to the invention for a flat web material, having associated pneumatic and control systems;

FIG. 2 shows, in a simplified illustration, the two roller registers of the buffer store of FIG. 1 together with the flat material tensioned between these roller registers.

The figures show, identified as 1, a roll or buffer store for intermediate storage of a length of flat web material 2 guided through said buffer store 1. The flat web material is, for example, a packaging material or a packaging film.

The buffer store 1 is then, for example, a component part of a system for packaging objects and is arranged upstream in said system in the advance or conveying direction A of the flat material 2 of a packaging machine.

The buffer store 1 essentially comprises two roller registers 3 and 4 of which the roller register 3 is fixed and the roller register 4 is movable relative to the roller register 3. In the embodiment shown, the roller register 4 is provided on a pivot frame 5 which is articulated via a joint 6 to a frame element 7 of the buffer store 1, specifically pivotable about an axis parallel to the surfaces of the flat material 2 which is guided through the buffer store 1 and perpendicular to the longitudinal extent of said material or perpendicular to the advance and conveying direction A. In order to tension the flat material 2 between the roller registers 3 and 4 by pivoting the pivot frame 5 about the axis of the joint 6 (arrow B), a pneumatic cylinder 8 is provided which acts between an arm 5.1 of the pivot frame 5 oriented radially to the axis of the joint 6, and a frame element 9 of the buffer store 1. For this purpose, the pneumatic cylinder 8 is articulated with the piston rod 8.1 thereof to the arm 5.1 and the cylinder 8.2 thereof is articulated to the frame element 9. By applying the pressure of a compressible fluid or pressure medium, e.g. compressed air, to the cylinder chamber 10 of the pneumatic cylinder 8, the pneumatic cylinder 8 acts by pivoting the pivot frame 5 out of the starting position shown in FIG. 1 upwardly in the direction of the arrow B, about the axis of the joint 6. By relieving or venting the cylinder chamber 10, the pivot frame 5 moves back under the weight thereof into the horizontal or substantially horizontal starting position thereof, as shown in FIG. 1.

Each of the roller registers 3 and 4 comprises a plurality of rollers 11 and 12 which are mounted at both ends freely rotating on bearing elements, specifically such that the rollers 11 and 12 are oriented with their axes parallel to one another and parallel to the axis of the joint 6, the rollers 11 of the roller register 3 and the rollers 12 of the roller register 4 being spaced apart from one another. Furthermore, the rollers 11 and 12 are arranged on the roller registers 3 and 4 or on the bearing elements 13 there such that in the starting position of the pivot frame 5, in the longitudinal direction of the flat material 2, a roller 12 alternates with a roller 11 in each case and the rollers 12 of the roller register 4 are situated at a level beneath the rollers 11 of the roller register 3. This arrangement of the rollers 11 and 12 in the lower position or starting position of the pivot frame 5 enables particularly easy threading of the flat web material through the buffer store 1. The rollers 11 and 12 are each adapted to the width of the flat web material 2 in the manner of a drum.

The bearing elements for the rollers 12 of the movable roller register 4 or for the axes of these rollers are formed, in the embodiment shown, by extensions 5.2.1 of two arms 5.2 which accommodate the rollers 12 therebetween and are offset relative to one another in an axis direction toward the drawing plane of FIG. 1, and form part of the pivot frame 5 comprising the roller register 4. The bearing elements for the rollers 11 are identified with the reference sign 13.

During normal operation, the cylinder chamber 10 of the pneumatic cylinder 8 has the operating pressure of the compressible fluid (e.g. compressed air) in the order of 2-3 bar applied thereto, so that the pivot frame 5 is pivoted out of the starting position thereof and the flat web material is guided in tensioned manner between the roller registers 3 and 4. The pneumatic cylinder 8 therefore acts as a gas spring which pretensions the pivot frame 5 in the direction of the arrow B. The length of flat material 2 stored in the buffer store 1 can be altered by pivoting the pivot frame 5 by means of the gas spring or against the action of said gas spring.

During normal operation, the buffer store 1 and, in particular, the pivot frame 5 and the movement space thereof are protected against access by a protective device 15, which is locked before the system or the buffer store 1 is put into operation and, particularly, before the operating pressure is applied to the cylinder chamber 10, by suitable, for example, pneumatic locking devices.

A peculiarity of the buffer store 1 lies therein that, in the case of a machine standstill, for example, when the system is switched off for processing the flat material 2, in the event of a fault, particularly on tearing of the flat web material 2, when said material is changed, etc., the pressure medium is trapped in the cylinder chamber 10 and then the pressure of said pressure medium in the cylinder chamber 10 is reduced to a residual pressure which lies significantly below the operating pressure, but is still sufficient to hold the pivot frame 5 against the weight thereof in a pivot position which corresponds to the pivot position of the pivot frame 5 before the machine standstill or the fault and in which the flat material guided through the roller registers 3 and 4 is still tensioned to some extent, i.e., for example is still tensioned such that the flat material still just runs flat or substantially flat between the rollers 11 and 12.

This control of the buffer store 1 and of the pneumatic cylinder 8 has significant advantages, particularly with regard to a substantial improvement in operating safety and ease of use of the buffer store 1. Trapping of the pressure medium in the cylinder chamber 10 and reducing the pressure therein, in the event of a machine standstill or a fault, to the much lower residual pressure, initially prevents unwanted jerking upward of the pivot frame 5, and thereby the risk of serious injury should the flat web material tear or be removed. Furthermore, the residual pressure in the cylinder chamber 10 holds the pivot frame 5 and the roller register 4 in a pivot position so that in this position the course of the flat material 2 through the roller registers 3 and 4 can be checked. The residual pressure is preferably adjusted so that, on tearing of the flat material and the subsequent relieving of the pivot frame 5 and expansion of the cylinder chamber 10, the residual pressure is further reduced, for example, to a value of 0.5 bar. The pivot position then assumed by the pivot frame 5 due to the weight thereof differs only slightly from the pivot position which the pivot frame 5 had assumed before the tearing of the flat web material 2 and jerking upward of the pivot frame 5 is effectively prevented.

The residual pressure also prevents unwanted automatic pivoting of the pivot frame 5 into the lower starting position thereof. The course followed by the flat material within the buffer store 1 before the machine standstill or the fault is maintained.

If the reduction of the pressure in the cylinder chamber 10 is carried out by venting via a relief valve or safety valve which opens at a pressure above the residual pressure that is striven for and blocks at the residual pressure and at a pressure below the residual pressure, the possibility still exists for pressing the pivot frame 5 manually downwardly in the direction of the lower starting position thereof, for example, for threading in the flat material 2.

In order to control the pneumatic cylinder 8, a control device 16 is provided, which comprises, in series in a line or connection connecting the cylinder chamber 10 to a source for the pressure medium (e.g. compressed air):

-   -   a preferably adjustable pressure controller 17,     -   a first multi-way control valve 18,     -   a second multi-way control valve 19,     -   a throttle 20 and     -   a non-return valve 21 which is arranged parallel to the throttle         20 and opens for flow out of the cylinder chamber 10 and blocks         flow in the opposing direction, so that the flow is guided via         the throttle.

In normal operation, i.e. with the flat material 2 tensioned between the roller registers 3 and 4 by means of the pneumatic cylinder 8, the control valves 18 and 19 are switched so that the constant operating pressure which exists at the output of the pressure controller 17 is applied via said control valves and the throttle 20 to the cylinder chamber 10. The possibility then also exists, with the protective device 15 closed, through suitable control of the control valve 18 to vent the cylinder chamber 10 via the non-return valve 21, the control valve 19 and a venting line 22 opened via the control valve 18 or to vent the cylinder chamber 10 via a throttle/non-return valve combination 23 and a venting filter 24 provided in said venting line, in order to pivot the pivot frame 5 into the lower starting position, for example, to guide or thread in a new web of the flat material 2, or to relieve the web of flat material 2 entirely in the region of the buffer store 1 or operatively to remove the buffer store 1 from the system.

In the event of a machine standstill or a fault or before opening the protective device 15, the control valve 19 is switched so that said valve separates the connection to the control valve 18 and essentially connects the cylinder chamber 10 via the non-return valve 21 to a relief valve or safety valve 25, which causes relief or venting of the cylinder chamber 10 to the residual pressure to which the safety valve 25 is set, for example, to the residual pressure of approximately 1 bar.

In order to maintain the residual pressure in the cylinder chamber 10 in the event of a fault in the source supplying the pressure medium or in the pressure medium feed, the control valve 19 can be actuated, for example, pneumatically.

The invention has been described above using exemplary embodiments. It should be understood that numerous alterations and variations are possible without departing from the fundamental inventive concept on which the invention is based.

REFERENCE SIGNS

-   1 Buffer store -   2 Flat web material -   3,4 Roller register -   5 Pivot frame -   5.1 Arm -   5.2 Arm of pivot frame -   5.2.1 Extension of arm 5.2 -   6 Joint -   7 Machine frame -   8 Pneumatic cylinder -   8.1 Piston rod -   8.2 Cylinder -   9 Machine frame -   10 Cylinder chamber -   11,12 Roller or drum -   13 Bearing element -   15 Protective or blocking device -   16 Control device -   17 Pressure controller -   18,19 Control valve -   20 Throttle -   21 Non-return valve -   22 Venting line -   23 Throttle/non-return valve arrangement -   24 Venting filter -   25 Safety valve -   A Advance and conveying direction of flat web material 2 -   B Pivot movement of the pivot frame 5 

1. A buffer store for a flat web material, said buffer store comprising at least two roller registers, said roller registers having a plurality of freely rotatable rollers and being movable relative to one another at least in an axis direction radial to an axis of the rollers thereby forming variable partial lengths or loops of the flat web material between the rollers of the roller registers, at least one piston-cylinder arrangement having a cylinder chamber for containing a compressible pressure medium, said piston-cylinder arrangement acting as a spring between the at least two roller registers in order to generate a web tension in the flat material guided through the buffer store, and a control device for applying a constant or substantially constant operating pressure of the pressure medium to the at least one piston-cylinder arrangement, the control device having a first control valve arrangement that switches between a first condition, for normal operation, and a second condition, for operation during a machine standstill and/or a fault, wherein, in the first condition, the control valve arrangement connects the cylinder chamber of the at least one piston-cylinder arrangement to a device for providing the constant or substantially constant operating pressure, and in the second condition, the control valve arrangement closes the cylinder chamber of the at least one piston-cylinder arrangement and connects said cylinder chamber to a relief valve that relieves pressure in the cylinder chamber to a residual pressure that is significantly smaller than the operating pressure.
 2. The buffer store according to claim 1, wherein the relief valve comprises a valve or safety valve that opens at a pressure above the residual pressure and blocks at a pressure that is equal to or smaller than the residual pressure.
 3. The buffer store according to claim 1, wherein the residual pressure is set to approximately 30% to 40% of the operating pressure.
 4. The buffer store according to claim 1, wherein the residual pressure is adjusted on the basis of the mass of the pivot frame.
 5. The buffer store according to claim 1, wherein the residual pressure is adjusted to approximately 1 bar.
 6. The buffer store according to claim 2, wherein the residual pressure is adjusted on the basis of the mass of the pivot frame.
 7. The buffer store according to claim 1, further comprising a throttle with a non-return valve arranged parallel to said throttle, said throttle being provided in the connection between the control valve arrangement and the piston-cylinder arrangement, said non-return valve opening for flow out of the cylinder chamber of the at least one piston-cylinder arrangement and blocking flow in the opposing direction.
 8. The buffer store according to claim 1, wherein the control valve arrangement is controllable by the pressure of the pressure medium such that, in the absence of pressure from the pressure medium, said control valve arrangement assumes the second condition thereof.
 9. The buffer store according to claim 1 wherein the device for providing the operating pressure comprises a pressure controller.
 10. The buffer store according to claim 1, further comprising at least one second control valve arrangement that is controllable between at least a first condition and a second condition, wherein said first condition connects the cylinder chamber of the at least one piston-cylinder arrangement to the device for providing the pressure medium at operating pressure, and said second condition vents the cylinder chamber into the atmosphere.
 11. The buffer store according to claim 10, wherein the first and/or second control valve arrangements are formed from at least one control valve.
 12. The buffer store according to claim 1, according to one of the preceding claims, wherein one roller register is fixed and one roller register is movable.
 13. The buffer store according to claim 1, wherein at least one roller register is a movable roller register provided on a pivot frame, and wherein the at least one piston-cylinder arrangement acts between the pivot frame or an arm of the pivot frame and a machine frame element of the buffer store.
 14. The buffer store of claim 1, wherein the piston-cylinder arrangement is configured to act as a gas spring.
 15. The buffer store of claim 1, wherein the piston-cylinder arrangement is configured to act as a compression spring.
 16. The buffer store of claim 7, wherein the throttle comprises an adjustable throttle. 